Well, for the example screenshots that you posted, the RawTherapee "exposure" controls consist of a number of things which darktable dedicates several distinct modules to.

• The "exposure" slider in darktable would be equivalent to the "exposure compensation" slider in RawTherapee, both giving values in EV. I'm guessing the "black" controls are equivalent as well, but use different units (don't know exactly what units in either case) for measuring black point adjustment.

• The RawTherapee documentation describes the "lightness" control as applying "a hard-coded tone curve to lift or lower the tonalities of the photo, resulting in a more or less light image". Not exactly sure if there's an equivalent in darktable... maybe adjusting only the middle point of the levels or curves module?

• For highlight and shadow compression, you'll want to see the "shadows and highlights" module in darktable.

• There's a module for "contrast brightness saturation" in darktable, but it's probably rarely used because of the sheer number of better options for adjusting all of those things. You may want to use it at first to avoid being overwhelmed, and ease into the more sophisticated modules as you find yourself wanting more control of certain things.

The module section of the darktable manual gives an overview of what they're each used for. While both are very capable of producing good results, the workflow with each of these two great software projects is quite different from the other, particularly in terms of applying similar processing to batches of images, and you'll probably find that you prefer one or the other based on that...